The present invention relates to a very-high pressure generator. More specifically, the invention relates to a very-high pressure generator for synthesizing diamonds, elucidating phenomena under very high pressure, and so on.
A very-high pressure generator with conventional DIA-type guide blocks will first be described. As shown in FIG. 13, the very-high pressure generator comprises a lower guide block 101, an upper guide block 102 disposed downward, a lower base plate 103 set at the center on the lower guide block 101, a lower anvil 104 set on the lower base plate 103, an upper base plate 105 set downward at the center on the upper downward guide block 102, an upper anvil 106 set on the top of the upper downward base plate 105, four slide blocks 107 which are pressed inward by four slopes of an upside-down pyramidal recess formed in the top surface of the lower guide block 101 and four slopes of a pyramidal recess formed in the top surface of the upper downward guide block 102, and four side anvils 108 set laterally inward on the inner sides of the four slide blocks 107.
The slopes of the pyramidal recesses of the lower and upper guide blocks 101 and 102 and the slopes of pyramidal portions of the slide blocks 107 are designed so as to make the reduction rate of the face-to-face distances between two side anvils 108 opposite to each other and between the other two side anvils 108 opposite to each other equal to the reduction rate of the face-to-face distance between the lower and upper anvils 104 and 106 under increasing pressure of the press. The six anvils 104, 106, and 108 are generally so arranged that their front end surfaces form a cubic pressurizing space where a pressure-transmitting medium is placed. Accordingly, by placing a pressure-transmitting medium in the space formed by the six anvils 104, 106, and 108 and pressing the lower and upper guide block 101 and 102 with a press ram, the pressure-transmitting medium is pressurized.
If the above conventional DIA-type guide blocks and a cell formed by sintered diamonds are combined to do a pressurizing experiment, the following two technical challenges have to be met.
(1) Raising the Rigidity of the Guide Blocks
It is necessary to raise the rigidity of the lower and upper guide blocks 101 and 102 so as to pressurize a pressure-transmitting medium, keeping the face-to-face distances between the anvils 104, 106, and 108 uniform.
(2) Raising the Rigidity of the Press
The difference between the deformation of the lower guide block 101 and that of the upper guide block 102 has to be minimized by uniforming the supporting conditions of the lower and upper guide blocks 101 and 102 as far as possible.
The above challenges can be met by increasing the size of the guide blocks 101 and 102 and the press frame, which, however, poses the following problems.
(1) Large-sized guide blocks
    (i) If the dimensions (thickness) of the guide blocks 101 and 102 are increased, the deformation of the surface areas of the guide blocks 101 and 102 supporting the base plates 103 and 105 increases due to the pressure exerted by the base plates 103 and 105 supporting the anvils 104 and 106 as shown by reference sign “X” in FIG. 14. Besides, the deformation is not even in the surface areas under the base plates 103 and 105, which may affect the cell formed by diamonds. Moreover, the deformation increases as the requirement for pressure increases.    (ii) If the guide blocks 101 and 102 are made wider and deeper while their height is left unchanged, the bending moment on the guide blocks 101 and 102 due to the pressure on the slopes of the pyramidal recesses of the guide blocks 101 and 102 exerted by the slide blocks 107 does not decrease, and hence the deformation of the slopes (change of angle of inclination of the slopes) hardly decreases. In other words, as shown by reference sign “Y” in FIG. 14, large stress due to the bending moment acts on the lines where the slopes meet the flat bottom, causing large strain. The angle of inclination of the slopes decreases as the load on the guide block increases (as shown in phantom in dash-double dot lines); accordingly, the design geometrical travel of the slide blocks 107, which could be attained if no deformation occurred, can not be attained.
Therefore, the necessary precision can be secured only in experiments where guide blocks with enough rigidity (oversized guide blocks) are used under relatively small pressure up to 1,000 tons or so.
(2) Large-sized press
    (i) It is possible in principle to reduce the deformation of the surface areas of the lower and upper guide blocks 101 and 102 supporting the lower and upper base plates 103 and 105 by increasing the size of the press, but it poses the problem of increased weight of the press. Besides, such a press requires large bearing power of the ground and is large in height.    (ii) In addition, special consideration is required to uniform the support conditions of all the anvils 104, 106, and 108 and thereby make the macroscopic deformation of each guide block even.
Accordingly, it would be very difficult to increase the rigidity of the lower and upper guide blocks 101 and 102 by increasing the size of the press so long as the present design of DIA-type guide blocks is applied to the very-high pressure generator under various preconditions.
The very-high pressure generator currently in use has the following further problems due to the configuration and structure of the lower and upper guide blocks 101 and 102.
(3) Assuming that the lower guide block 101 is on the ram side and the upper guide block 102 is on the frame side, the pressure acts on the six anvils 104, 106, and 108 through the lower guide block 101 and the reaction acts on the six anvils 104, 106, and 108 through the upper guide block 102. The portion of the upper guide block 102 supporting the base plate 105 of the upper anvil 106 is pressed vertically upward by the pressure; accordingly compressive stress occurs in the portion. The portion of the lower guide block 101 supporting the base plate 103 of the lower anvil 104 is pressed vertically downward by the reaction; accordingly compressive stress occurs in the portion. On the other hand, each slope of the pyramidal recess of the upper guide block 102 is pressed perpendicularly thereto by the pressure transmitted through a corresponding slope of a corresponding slide block 107. Each slope of the pyramidal recess of the lower guide block 101 is pressed perpendicularly thereto by the reaction transmitted through a corresponding slope of a corresponding slide block 107. Thus, compressive stress and bending stress occur in the slope portions and their adjacent portions of the upper and lower guide block 102 and 101. In other wards, the lower and upper anvils 104 and 106 are supported more rigidly than the side anvils 108; therefore, the lower and upper anvils 104 and 106 advance more than the side anvils 108 under increasing pressure.
(4) If the machining error of one of the lower and upper guide blocks 101 and 102, the slide blocks 107, and the six anvils 104, 106, and 108 goes over the tolerance, the rates of change of the face-to-face distances of the three pairs of anvils under increasing pressure become uneven.
In accordance with the above, the object of the present invention is to provide a very-high pressure generator of construction such that the lower and upper guide blocks of the generator are each configured so as to form a pyramidal recess on the bottom surface and an upside-down pyramidal recess on the top surface accurately symmetrically, their pyramidal slopes given one and the same angle of inclination, and are prevented from being deformed under high pressure not by enlarging the guide blocks and the press, but by making the support conditions of all the anvils of the generator uniform, the positions of the anvils can easily be adjusted, and therefore the generator is capable of pressurizing a pressure-transmitting medium into the shape of a desired cube accurately.